Reductant delivery unit for automotive selective catalytic reduction with thermally optimized peak-and-hold actuation based on an injector open event

Abstract

A trigger circuit is provided for a peak and hold driver circuit for a reductant delivery unit (RDU) having a solenoid-operated injector for selective catalytic reduction (SCR) after-treatment for vehicles. The peak and hold driver circuit is constructed and arranged to actuate the injector in a rise-to-peak current phase followed by a low current hold phase. The trigger circuit includes an injector open detection circuit constructed and arranged, based on a detected opening event of the injector, to trigger a transition from the rise-to-peak phase to the subsequent hold phase of the injector.

What is claimed is: 
     
         1 . A trigger circuit for a peak and hold driver circuit for a reductant delivery unit (RDU) having a solenoid-operated injector for selective catalytic reduction (SCR) after-treatment for vehicles, the peak and hold driver circuit being constructed and arranged to actuate the injector in a rise-to-peak current phase followed by a low current hold phase, the trigger circuit comprising:
 an injector open detection circuit constructed and arranged, based on a detected opening event of the injector, to trigger a transition from the rise-to-peak phase to the subsequent hold phase of the injector.   
     
     
         2 . The trigger circuit of  claim 1 , in combination with the driver circuit so that the driver circuit includes the trigger circuit. 
     
     
         3 . The combination of  claim 2 , in further combination with the RDU. 
     
     
         4 . The combination of  claim 3 , wherein the driver circuit and trigger circuit are part of a control unit electrically connected with the RDU. 
     
     
         5 . The trigger circuit of  claim 1 , wherein the open detection circuit is constructed and arranged to trigger the transition based on an electrical pulse generated upon detecting the opening event of the injector by using a second derivative of a current waveform as an input. 
     
     
         6 . The trigger circuit of  claim 5 , wherein the open detection circuit includes a differentiating circuit. 
     
     
         7 . A reductant delivery unit (RDU) and control unit for selective catalytic reduction (SCR) after-treatment for vehicles, the RDU and control unit comprising:
 an RDU having a solenoid-operated injector, and   a control unit electrically connected with the injector, the control unit having a peak and hold driver circuit constructed and arranged to actuate the injector in a rise-to-peak current phase followed by a low current hold phase, the driver circuit including an injector open detection circuit constructed and arranged, based on a detected opening event of the injector, to trigger a transition from the rise-to-peak phase to the subsequent hold phase of the injector.   
     
     
         8 . The RDU and control unit of  claim 7 , wherein the injector open detection circuit is constructed and arranged to trigger the transition based on an electrical pulse generated upon detecting the opening event of the injector by using a second derivative of a current waveform as an input 
     
     
         9 . The RDU and control unit of  claim 8 , wherein the injector open detection circuit includes a differentiating circuit. 
     
     
         10 . A method of triggering a reductant delivery unit (RDU) having a solenoid-operated injector for selective catalytic reduction (SCR) after-treatment for vehicles, the method comprising:
 detecting an opening event of the injector, and   based on the detecting, step, triggering a transition from a rise-to-peak phase to a subsequent hold phase of the injector, thereby limiting a thermal load on the injector to a minimum required to ensure opening of the injector.   
     
     
         11 . The method of  claim 10 , wherein the detecting step uses a second derivative of a current waveform of the injector.